The present invention relates to an integrated circuit comprising a circuit board in which a conductive layer having a desired pattern is formed on a metal substrate through an insulating layer, and a circuit element nondetachably mounted on the insulating layer and having a nonvolatile storage content which can be rewritten by an external operation.
Conventionally, a technique disclosed in Japanese Patent Publication No. 46-13234 is known as an integrated circuit having a pair of metal substrates, wherein conductive layers are adhered to the metal substrates through insulating layers, a circuit element is fixed to each conductive layer, and the conductive layers are connected through a connecting substrate, and are separated from each other to face each other. A method of manufacturing the integrated circuit disclosed in this prior art comprises the step of anode-oxidizing at least one major surface of an aluminum substrate to form a thin aluminum oxide layer on the substrate surface, the step of selectively bonding and forming a resistive material and a high-conductivity material on the thin aluminum oxide film to form a plurality of circuit elements, the step of fixing transistor pellets on lead portions formed by selectively bonding the high-conductivity material, and the step of sealing at least all the circuit elements with an insulating resin.
In the integrated circuit formed in this manner, on a circuit board in which a conductive layer of a desired pattern is formed on a metal substrate through an insulating layer, at least one memory element is nondetachably mounted as a so-called bare chip on the insulating layer.
The integrated circuit formed in this manner can quickly and effectively dissipate heat generated from resistors or transistors during an operation, thus realizing an integrated circuit of, e.g., an output circuit.
The integrated circuit formed in this manner may be employed in a vehicle in view of its compact structure and low cost. However, when the integrated circuit having a metal substrate is actually used in a vehicle, a circuit element comprising a logic processing unit mounted on the integrated circuit, i.e., a CPU has been developed. The CPU has a first logic processing content as a function of a predetermined engine control unit in an engine drive state, and a second processing content as a diagnostic function in a maintenance state, which can be selectively used.
In order to selectively execute one of at least two different logic processing contents of the logic processing unit, a special-purpose switching terminal for switching these functions must be equipped, and must be arranged outside the integrated circuit. This structure may pose a problem of a complicated structure.